Single polarization optical fibers

Abstract

Since the single polarization optical fiber according to the present invention comprises a core which does not substantially contain a dopant such as Ge, P or the like as well as a transition metal such as Fe, Cu or the like, the fiber has favorable radiation resistance, besides there is no decrease in refractive index at the central portion of the core, when the fiber is fabricated in accordance with an inner CVD method. It is also possible to decrease a vapor deposition temperature in the inner, CVD method by causing trace amounts of B.sub.2 O.sub.3 to be present in the core. Further since the cladding of the optical fiber is constituted of high-purity SiO.sub.2 containing fluorine or a mixture of fluorine and B.sub.2 O.sub.3, the total thickness of the cladding and the inner jacket can be reduced in the case where high-purity SiO.sub.2 is utilized as the core so that the fabrication thereof can easily be effected. Since the optical fiber is constituted so as to satisfy the relationship n.sub.1 >n.sub.3 >n.sub.2 (refractive index n.sub.1 of the core, refractive index n.sub.2 of the cladding, and refractive index n.sub.3 of the inner jacket), the resulting optical fiber is not affected by variations in the core and in addition, connection of the optical fibers can easily be effected by increasing the core diameter thereof while such optical fiber maintains a stable single-mode operation wavelength band along the longitudinal direction thereof.